Polyurethanes made using bismuth thiocarbamate or thiocarbonate salts as catalysts

ABSTRACT

Polyisocyanate-based polymers are formed by curing a reaction mixture containing at least one polyisocyanate and at least one isocyanate-reactive compound having at least two isocyanate-reactive groups in the presence of a bismuth mono- or dithiocarbamate or mono- or dithiocarbonate salt.

This invention relates to processes for making polymers frompolyisocyanates and isocyanate-reactive materials. The invention isparticularly applicable to making cast polyurethane elastomers.

Many solid or microcellular polyurethane elastomers are manufacturedusing cast elastomer methods. These elastomers are made by reacting ahigh equivalent weight polyol and a chain extender material with apolyisocyanate compound. Because it is usually intended to form a highlyflexible, rubbery product, the amount of chain extender in theformulation is usually somewhat small. The elastomer is produced bymixing the starting materials and transferring the mixture into a moldwhere it is cured, usually with application of heat. Some or all of thehigh equivalent weight polyol may be pre-reacted with the polyisocyanatein a preliminary step to form an isocyanate-terminated prepolymer orquasi-prepolymer. Such a prepolymer is then caused to react with thechain extender and optionally a remaining portion of the high equivalentweight polyol during the molding step.

Open time is very important in cast elastomer processes. Once thestarting materials are mixed, they must remain in an uncured, flowablestate for several minutes to allow the mixture to be degassed (in mostcases) and transferred into the mold. If the reaction proceeds tooquickly, the mold may not fill completely and/or flow lines or otherdefects can appear in the parts, which can lead to high reject rates.

Once the mold is filled, however, a rapid cure is wanted, to reducecycle times and maximize mold usage.

Organomercury compounds are often the catalysts of choice for castelastomer processes. Organomercury catalysts offer an importantcombination of attributes that have proven to be extremely difficult toduplicate with other catalyst systems. These organomercury catalystsprovide a very desirable curing profile in which a long open time isfollowed by a rapid cure. A second attribute of organomercury catalystsis that they produce polyurethane elastomers that have very desirablephysical and mechanical properties.

Mercury catalysts are undesirable from an environmental and workerexposure standpoint, and in many jurisdictions these are being phasedout. Therefore, a replacement catalyst system is needed. Such areplacement catalyst system ideally would provide the attributes oforganomercury catalysts, including a desirable cure profile, goodproperty development in the product, and good surface appearance.

Various bismuth compounds have been described as polyurethane catalysts.Bismuth carboxylates, for example, are described in U.S. Pat. No.3,714,077 (polyurethane foam systems), U.S. Pat. No. 4,584,362 (as solecatalysts in polyurethane elastomer systems) and U.S. Pat. No. 5,011,902(in admixture with other metallic catalysts in plywood patch systems).As mentioned in WO 2005/058996, those bismuth catalysts by themselvesare too reactive and lead to short pot life when used in polyurethaneelastomer systems. In addition, WO 2005/058996 reports that thesecatalysts tend to lose activity when stored in a polyol. WO 2005/058996purports to address these problems by using a bismuth catalyst togetherwith certain titanium, zirconium, hafnium, iron, cobalt or aluminumcatalysts.

Other bismuth catalysts that have been described include bismuthmercaptides (e.g., U.S. Pat. No. 4,788,083 and U.S. Pat. No. 6,348,121)and bismuth alkoxides (e.g., U.S. Pat. No. 3,714,077).

This invention is in one aspect a process for preparing apolyisocyanate-based polymer, comprising forming a reaction mixturecontaining at least one polyisocyanate, at least one isocyanate-reactivecompound having at least two isocyanate-reactive groups and at least onecatalyst, and then curing the reaction mixture to form a polymer,wherein the catalyst includes a bismuth salt of a mono- ordithiocarbamate compound, a bismuth salt of a mono- or dithiocarbonatecompound, or a mixture of two or more such bismuth salts.

These bismuth salts have been found to provide long open times in manypolyurethane systems, followed by a very rapid cure. Unlike otherbismuth compounds, these bismuth salts are very useful catalysts forcast polyurethane elastomer systems and other polyurethane systemsrequiring a long open time, even when used by themselves as the solecatalyst in such systems.

In addition, polymer properties are obtained that are very similar tothose provided by the mercury catalysts.

A polymer is prepared in accordance with the invention by forming amixture of at least one organic polyisocyanate compound, at least oneisocyanate-reactive material that reacts at least difunctionally withisocyanate groups and the bismuth salt, and curing the mixture to formthe polymer. Curing is achieved by subjecting the mixture to conditionssufficient for the organic polyisocyanate compound and the isocyanatereactive material to react to form the polymer. The polymer will in mostcases contain one or more of urethane linkages, urea linkages,allophanate linkages, biuret linkages, isocyanurate linkages, amidelinkages, oxazolidone linkages, or some of two or more of these types oflinkages.

The catalyst is a bismuth salt of a mono- or dithiocarbamate compound ormono- or dithiocarbonate compound (or a mixture of two or more thereof).Mono- or dithiocarbamate compounds include those represented bystructure I:

wherein X is sulfur or oxygen, X¹ is sulfur or oxygen, provided that atleast one of X and X¹ is sulfur, and each R¹ is independently ahydrocarbyl group that may be substituted with one or moreheteroatom-containing substituent groups, provided that the R¹ groupstogether may form an unsubstituted or inertly substituted divalentorganic radical that completes a ring structure with the N atom. Whenonly one of X and X¹ is sulfur, the compound is a monothiocarbamate.When both X and X¹ are sulfur, the compound is a dithiocarbamate.

Mono- or dithiocarbonate compounds include those represented bystructure II:

wherein X and X¹ are as defined with respect to structure I, and R¹ ahydrocarbyl group that may be substituted with one or moreheteroatom-containing substituent groups. When only one of X and X¹ issulfur, the compound is a monothiocarbonate. When both X and X¹ aresulfur, the compound is a dithiocarbonate.

In structures I and II, the R¹ group(s) may be linear, branched and/orcyclic hydrocarbon groups. The R¹ groups may be unsaturated orsaturated. Thus, the R¹ groups may be alkyl, alkenyl, alkynyl,cycloalkyl, aryl, aryl-substituted alkyl, alkyl-substituted aryl and thelike. The R¹ group(s) each may contain, for example, from 1 to 30,especially from 4 to 18 carbon atoms. The R¹ group(s) may contain one ormore heteroatom-containing substituents. Those heteroatom-containingsubstituent(s) preferably do not bond or complex with the bismuth atom.Examples of suitable heteroatom-containing substituents include ether,hydroxyl, carbonate, ester, carbamate, tertiary amine, urea, urethane,imine, halogen and the like.

In structure I and structure III below, the two R¹ groups may togetherform a divalent organic radical that completes a ring structure with thenitrogen atom.

The bismuth salt of the mono- or dithiocarbamate includes thoserepresented by structure III:

where X, X¹ and R¹ are as defined with respect to structure I, n is anumber from 1 to 3, and each L is independently an anion other than amono- or dithiocarbamate anion. The X¹ sulfur or oxygen may coordinateto the bismuth atom. n preferably is at least 2 and more preferably is3.

The bismuth salt of the mono- or dithiocarbonate includes compoundsrepresented by structure IV:

where X, X¹, R¹, L and n are as defined with respect to structure II. Asbefore, the X¹ sulfur or oxygen may coordinate to the bismuth atom. n instructure IV may be at least 2 and is 3 in some embodiments.

The L group(s), when present, may be for example, halogen, alkoxide,aryloxy, carboxylate, alkylmercaptide, phenolate, amide, alkylsulfonate,trifluoromethylsulfonate (triflate), bis(trialkylsilyl)amide,hexamethyldisilazide, phosphate or hydrocarbyl. Two or more differentanions L may be present.

The bismuth thiophosphoric acid diester salt may be provided in the formof a solution of a suitable solvent such as a hydrocarbon and/oralcohol.

The organic polyisocyanate contains an average of at least 1.5 andpreferably at least 2.0 isocyanate groups per molecule. Thepolyisocyanate(s) may contain an average of as many as 8 isocyanategroups per molecule, but typically contain no more than about 4isocyanate groups per molecule on average. The organic polyisocyanatemay contain as little as 0.5% by weight isocyanate groups, or maycontain as much as about 50% by weight isocyanate groups. The isocyanategroups may be bonded to aromatic, aliphatic or cycloaliphatic carbonatoms. Examples of polyisocyanates include m-phenylene diisocyanate,toluene-2,4-diisocyanate, toluene-2,6-diisocyanate,hexamethylene-1,6-diisocyanate, tetramethylene-1,4-diisocyanate,cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate,naphthylene-1,5-diisocyanate, methoxyphenyl-2,4-diisocyanate,diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate,diphenylmethane-2,2′-diisocyanate, 4,4′-biphenylene diisocyanate,3,3′-dimethoxy-4,4′-biphenyl diisocyanate, 3,3′-dimethyl-4-4′-biphenyldiisocyanate, 3,3′-dimethyldiphenyl methane-4,4′-diisocyanate,4,4′,4″-triphenyl methane triisocyanate, a polymethylenepolyphenylisocyanate (PMDI), toluene-2,4,6-triisocyanate and4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate. Preferably thepolyisocyanate is diphenylmethane-4,4′-diisocyanate,diphenylmethane-2,4′-diisocyanate, PMDI, toluene-2,4-diisocyanate,toluene-2,6-diisocyanate or mixtures of any two or more thereof.Diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate andmixtures thereof are generically referred to as MDI, and all can beused. Toluene-2,4-diisocyanate, toluene-2,6-diisocyanate and mixturesthereof are generically referred to as TDI, and all can be used.

Any of the foregoing isocyanates can be modified to include urethane,urea, biuret, carbodiimide, allophanate, uretonimine, isocyanurate,amide or like linkages. Examples of modified isocyanates of these typesinclude various urethane group and/or urea group-containing prepolymers,some of which are described in more detail below, so-called “liquid MDI”products, and the like.

A wide range of isocyanate-reactive materials can be used to form thepolymer through reaction with the organic polyisocyanate. A suitableisocyanate-reactive material contains at least two hydrogen atoms thatare active according to the well-known Zerewitinoff active hydrogendetermination test. Isocyanate-reactive groups that contain activehydrogen atoms include aliphatic primary or secondary hydroxyl groups,aromatic hydroxyl groups, aliphatic or aromatic primary or secondaryamine groups, thiol (mercapto) groups, carboxylic acid groups, oxiranegroups and the like. An isocyanate-reactive material should contain atleast two such isocyanate-reactive groups. The isocyanate-reactivegroups on a particular isocyanate-reactive material may be all the same,or may be of two or more different types.

Various types of isocyanate-reactive materials can be used. One of theseis water, which is considered to be an isocyanate-reactive material forpurposes of this invention as it consumes two isocyanate groups toproduce a urea linkage, with elimination of a molecule of carbondioxide.

Another type of isocyanate-reactive material is a high equivalent weightisocyanate-reactive material that has a molecular weight of at least 250per isocyanate-reactive group. These high equivalent weightisocyanate-reactive materials are commonly used in making flexible andsemi-flexible polyurethane and/or polyurea polymers, which may benon-cellular, microcellular or foam materials. These high equivalentweight materials are also used as flexibilizers or tougheners for rigidfoamed or non-foamed polyurethane and/or polyurea polymers.

Various types of high equivalent weight isocyanate-reactive materialsare useful, including hydroxy-functional acrylate polymers andcopolymers, hydroxy-functional polybutadiene polymers, polyetherpolyols, polyester polyols, amine-terminated polyethers, and variouspolyols that are based on vegetable oils or animal fats. Polyetherpolyols include, for example, polymers of propylene oxide, ethyleneoxide, 1,2-butylene oxide, tetramethylene oxide, block and/or randomcopolymers thereof, and the like. Of particular interest for manyhigh-volume applications are poly(propylene oxide) homopolymers, randomcopolymers of propylene oxide and ethylene oxide in which theoxyethylene content is, for example, from about 1 to about 30% byweight, ethylene oxide-capped poly(propylene oxide) polymers whichcontain from 70 to 100% primary hydroxyl groups, and ethyleneoxide-capped random copolymers of propylene oxide and ethylene oxide inwhich the oxyethylene content is from about 1 to about 30% by weight.The polyether polyols may contain low amounts of terminal unsaturation(for example, less than 0.02 meq/g or less than 0.01 meq/g), such asthose made using so-called double metal cyanide (DMC) catalysts asdescribed for example in U.S. Pat. Nos. 3,278,457, 3,278,458, 3,278,459,3,404,109, 3,427,256, 3,427,334, 3,427,335, 5,470,813 and 5,627,120.Polymer polyols of various sorts may be used as well. Polymer polyolsinclude dispersions of polymer particles, such as polyurea,polyurethane-urea, polystyrene, polyacrylonitrile andpolystyrene-co-acrylonitrile polymer particles, in a polyol, typically apolyether polyol. Suitable polymer polyols are described in U.S. Pat.Nos. 4,581,418 and 4,574,137.

High equivalent weight isocyanate-reactive polyesters include reactionproducts of polyols, preferably diols, with polycarboxylic acids ortheir anhydrides, preferably dicarboxylic acids or dicarboxylic acidanhydrides. The polycarboxylic acids or anhydrides may be aliphatic,cycloaliphatic, aromatic and/or heterocyclic and may be substituted,such as with halogen atoms. The polycarboxylic acids may be unsaturated.Examples of these polycarboxylic acids include succinic acid, adipicacid, terephthalic acid, isophthalic acid, trimellitic anhydride,phthalic anhydride, maleic acid, maleic acid anhydride and fumaric acid.The polyols used in making the polyester polyols preferably have anequivalent weight of 150 or less and include ethylene glycol, 1,2- and1,3-propylene glycol, 1,4- and 2,3-butane diol, 1,6-hexane diol,1,8-octane diol, neopentyl glycol, cyclohexane dimethanol,2-methyl-1,3-propane diol, glycerine, trimethylol propane, 1,2,6-hexanetriol, 1,2,4-butane triol, trimethylolethane, pentaerythritol, quinitol,mannitol, sorbitol, methyl glycoside, diethylene glycol, triethyleneglycol, tetraethylene glycol, dipropylene glycol, dibutylene glycol andthe like. Polycaprolactone polyols are useful. Polymer polyols ofvarious sorts may be used as well.

High equivalent weight amine-terminated polyethers include polymers andcopolymers of propylene oxide, in which all or a portion of the terminalhydroxyl groups are converted to amino groups. The conversion to aminogroups can be performed in a reductive amination process in which thepolyether is reacted with hydrogen and ammonia or a primary amine.Amine-terminated polyethers of this type are commercially available fromHuntsman under the trade name Jeffamine®. Another type ofamine-terminated polyether is prepared by capping the terminal hydroxylgroups of a polyether with a diisocyanate to produce anisocyanate-terminated intermediate, and then hydrolyzing theisocyanate-terminal groups to form terminal aromatic amine groups.

High equivalent weight isocyanate-reactive materials based on vegetableoils and/or animal fats include, for example, castor oil, hydroxymethylgroup-containing polyols as described in WO 2004/096882 and WO2004/096883, amide group-containing polyols as described in WO2007/019063, hydroxyl ester-substituted fatty acid esters as describedin WO 2007/019051, “blown” soybean oils as described in US PublishedPatent Applications 2002/0121328, 2002/0119321 and 2002/0090488,oligomerized vegetable oil or animal fat as described in WO 06/116456,hydroxyl-containing cellulose-lignin materials, hydroxyl-containingmodified starches as well as the various types of renewable-resourcepolyols described in Ionescu, Chemistry and Technology of Polyols forPolyurethanes, Rapra Publishers 2005.

Another useful class of isocyanate reactive materials includes polyolsand aminoalcohols that contain at least three isocyanate-reactive groupsper molecule and have a molecular weight per isocyanate-reactive groupof up to 249, preferably from about 30 to about 200. These materials mayhave up to 8 or more isocyanate-reactive groups per molecule. They mosttypically include no more than one primary or secondary amino group, andtwo or more primary or secondary hydroxyl groups. This class ofisocyanate-reactive materials includes materials that are commonly knownas crosslinkers or (because they are commonly used in making rigidpolyurethane foams) “rigid polyols”. Examples of isocyanate-reactivematerials of this type include diethanolamine, triethanolamine, di- ortri(isopropanol) amine, glycerin, trimethylol propane, pentaerythritol,various polyester polyols that have at least three hydroxyl groups permolecule and an equivalent weight of up to 249, and various lowequivalent weight polyether polyols that have at least three hydroxylgroups per molecule. The low equivalent weight polyether polyolsinclude, for example, ethoxylates and/or propoxylates of an aromaticdiamine such as toluene diamine and phenylene diamine, an aliphaticdiamine such as ethylene diamine, cyclohexanedimethanol and the like, ora polyol having at least three hydroxyl groups, such as, for example,glycerin, sucrose, sorbitol, pentaerythritol, trimethylolpropane,trimethylolethane and the like.

Another class of suitable isocyanate-reactive materials includes chainextenders, which for the purposes of this invention means a materialhaving exactly two isocyanate-reactive groups per molecule and anequivalent weight per isocyanate-reactive group of up to 249, especiallyfrom 31 to 125. The isocyanate reactive groups are preferably hydroxyl,primary aliphatic or aromatic amine or secondary aliphatic or aromaticamine groups. Representative chain extenders include ethylene glycol,diethylene glycol, triethylene glycol, 1,2-propylene glycol,1,3-propylene glycol, 1,4-butane diol, 1,6-hexane diol, neopentylglycol, dipropylene glycol, tripropylene glycol, poly(propylene oxide)diols of up to 249 equivalent weight, cyclohexanedimethanol,poly(ethylene oxide) diols of up to 249 equivalent weight, aminatedpoly(propylene oxide) diols of up to 249 equivalent weight, ethylenediamine, phenylene diamine, diphenylmethane diamine,bis(3-chloro-4-aminophenyl)methane and 2,4-diamino-3,5-diethyl toluene.A mixture of chain extenders may be used.

The relative amounts of polyisocyanate and isocyanate-reactive materialsprovided to the reaction mixture are selected to produce a highmolecular weight polymer. The ratio of these components is typicallyexpressed as “isocyanate index” which for purposes of this inventionmeans 100 times the ratio of the equivalents of isocyanate groupsprovided by the isocyanate-reactive materials to the equivalents ofisocyanate-reactive groups provided by the isocyanate-reactivematerials. The isocyanate index is typically at least 50, and may be upto 1000 or more. When flexible or semi-flexible cellular, microcellularor non-cellular polymers are prepared, the isocyanate index is generallyfrom 70 to about 150 and more typically from about 70 to 125. Tighterranges may be used in specific cases. Rigid polymers such as structuralpolyurethanes and rigid foams are typically made using an isocyanateindex of from 90 to 200. Polymers containing isocyanurate groups areoften made at isocyanate indices of at least 150, up to 600 or more.

The reaction of the polyisocyanate with the isocyanate-reactivematerials may be performed all at once (a “one-shot” process), or can beconducted in stages through the formation of an isocyanate-terminatedprepolymer or quasi-prepolymer which is then reacted with additionalisocyanate-reactive material(s) to form the final polymer. The catalystof the invention can be present during the formation of a prepolymer orquasi-prepolymer, during the reaction of the prepolymer orquasi-prepolymer to form a final polymer, or both stages.

The bismuth salt is present in an amount sufficient to provide acommercially acceptable polymerization rate. A typical amount is from0.01 to 3 millimoles of the bismuth salt per kilogram of reactants(i.e., the polyisocyanate(s) and isocyanate-reactive materials) presentin the polymerization process, although amounts may vary depending onthe particular polymerization process and the particular reactants thatare present. A preferred amount is from 0.05 to 1 millimole of bismuthsalt per kilogram of reactants, and a more preferred amount is from0.075 to 0.5 millimole of bismuth salt per kilogram of reactants.

When used by itself, the bismuth salt provides for a long open time anda long cure time. It has been found that the cure time can be reducedvery substantially by including certain activator compounds in theformulation. Useful activators include aluminosilicates such asmolecular sieves and zeolites, as well as various inorganic or organicbases. Suitable inorganic bases include alkali metal salts of weakacids. An example of such an inorganic base is a sodium or potassiumsalt of a dithiophosphoric acid diester, such as sodium dithiophosphoricacid di(n-hexyl) ester.

A preferred type of organic base activator is a compound that containsone or more tertiary amino groups.

Representative tertiary amine-containing activator compounds include butare not limited to 1,8-diaminonaphthalene, trimethylamine,triethylamine, dimethylethanolamine, N-methylmorpholine,N-ethylmorpholine, N,N-dimethylbenzylamine, N,N-dimethylethanolamine,N,N,N′,N′-tetramethyl-1,4-butanediamine, N,N-dimethylpiperazine,tetramethylguanidine, 1,4-diazobicyclo-2,2,2-octane,bis(dimethylaminoethyl)ether, bis(2-dimethylaminoethyl)ether,morpholine, 4,4′-(oxydi-2,1-ethanediyl)bis, triethylenediamine,pentamethyl diethylene triamine, dimethyl cyclohexyl amine,N-cetyl-N,N-dimethyl amine, N-coco-morpholine, N,N-dimethyl aminomethylN-methyl ethanol amine, N,N,N′-trimethyl-N′-hydroxyethylbis(aminoethyl)ether, N,N-bis(3-dimethylaminopropyl)N-isopropanolamine,(N,N-dimethyl) amino-ethoxy ethanol, N,N,N′,N′-tetramethyl hexanediamine, N,N-dimorpholinodiethyl ether, N-methyl imidazole, dimethylaminopropyl dipropanolamine, bis(dimethylaminopropyl)amino-2-propanol,tetramethylamino bis(propylamine),(dimethyl(aminoethoxyethyl))((dimethyl amine)ethyl)ether,tris(dimethylamino propyl) amine, dicyclohexyl methyl amine,bis(N,N-dimethyl-3-aminopropyl) amine, 1,2-ethylene piperidine andmethyl-hydroxyethyl piperazine.

A preferred type of tertiary amine-containing activator compound is anamidine compound, which may be acyclic or cyclic. The amidine compoundcontains at least one —N═C—N< group, which may be incorporated into acyclic structure. This class of catalysts includes cyclic amidines suchas 2,3-dimethyltetrahydropyridimine, and bicyclic amidines such as1,8-diazabicyclo-5.4.0-undecene-7,1,5-diazobicyclo-4.3.0-nonene-5,6-dibutylamino-1,8-diazabicyclo-5.4.0-undecene-7and other substituted bicyclic amidine compounds.

Any of the foregoing tertiary amine catalysts, and the amidine catalystsin particular, may be present in the form of a salt, particularly aphenolate and/or carboxylate salt.

Tertiary amine compounds are known to catalyze the reactions ofisocyanate groups with alcohols. In this invention, it is preferred thatany tertiary amine activator compound or compounds be present in verysmall amounts, at which the tertiary amine compound exhibits very littleif any catalytic activity. A tertiary amine activator compound may bepresent, for example, in an amount ranging from 0.1 to 10 moles per moleof the bismuth salt, but not more than 10 millimoles of tertiary amineactivator per kilogram of reactants. A more preferred amount is from 0.5to 5 moles of tertiary amine activator per mole of the bismuth salt, anda still more preferred amount is from 0.5 to 3 moles of tertiary amineactivator per mole of the bismuth salt, but in each case not more than10 millimoles of tertiary amine activator per kilogram of reactants. Itis more preferred that no more than 5 millimoles of tertiary aminecatalyst compound(s), especially not more than 1 millimole of tertiaryamine activator compound(s), are present per kilogram of reactants.

Activators that do not possess catalytic activity may be present inlarger amounts, such as up to about 5% by weight, preferably up to about3% by weight, based on the weight of the reactants.

A wide variety of polymers can be made in accordance with the invention,through the proper selection of particular polyisocyanates,isocyanate-reactive materials, the presence of optional materials suchas are described below, and reaction conditions. The process of theinvention can be used to produce polyurethane and/or polyurea polymersof various types, including cast elastomers, flexible or semi-flexiblereaction injection molded parts (which may be reinforced and/or containfillers), rigid structural composites which contain reinforcementsand/or fillers, flexible polyurethane foams, which may be made inslabstock and/or molding processes, rigid polyurethane foams, sealantsand adhesives (including moisture-curable types), binders such as forpolymer concrete or for cushioning material such as playground or sportssurfaces, mats and the like, cushion and/or unitary backings for carpetand other textiles, semi-flexible foams, pipe insulation, automotivecavity sealing, automotive noise and/or vibration dampening,microcellular foams such as shoe soles, tire fillers, and the like.Processes for making polyurethane and/or polyureas of all of these typesare well known; conventional processing methods for making theseproducts are entirely suitable for use with this invention.

Depending on the particular type of polymer being produced and theneeded attributes of the polymer, a wide variety of additional materialsmay be present during the reaction of the isocyanate compound with theisocyanate-reactive materials. Among these materials are surfactants;blowing agents; cell openers; fillers; pigments and/or colorants;desiccants, reinforcing agents; biocides; preservatives; antioxidants;flame retardants; and the like.

One or more surfactants may be present, especially when some blowingagent is incorporated into the formulation. A surfactant can help tostabilize the cells of the composition as gas evolves to form bubbles. Asurfactant can also help to wet filler particles and in that way make iteasier to incorporate them into the system. Examples of suitablesurfactants include alkali metal and amine salts of fatty acids, such assodium oleate, sodium stearate, diethanolamine oleate, diethanolaminestearate, diethanolamine ricinoleate and the like; alkali metal andamine salts of sulfonic acids such as dodecylbenzenesulfonic acid anddinaphthylmethanedisulfonic acid; ricinoleic acid; siloxane-oxyalkylenepolymers or copolymers and other organopolysiloxanes; oxyethylatedalkylphenols (such as Tergitol NP9 and Triton X100, from The DowChemical Company); oxyethylated fatty alcohols such as Tergitol 15-S-9,from The Dow Chemical Company; paraffin oils; castor oil; ricinoleicacid esters; turkey red oil; peanut oil; paraffins; fatty alcohols;dimethyl polysiloxanes and oligomeric acrylates with polyoxyalkylene andfluoroalkane side groups. These surfactants are generally used inamounts of 0.01 to 2 parts by weight based on 100 parts by weight of thepolyols. Organosilicone surfactants are generally preferred types.Examples of commercially available surfactants that are useful includeDabco™ DC2585, Dabco™ DC5043 and Dabco™ DC5180 surfactants, availablefrom Air Products, Niax™ U-2000 surfactant, available from GE OSiSilicones, and Tegostab™ B 8681, Tegostab™ B4351, Tegostab™ B8631,Tegostab™ B8707 and Tegostab™ B8715 surfactants, available from Th.Goldschmidt.

A blowing agent may be present if it is desired to form a cellular ormicrocellular polymer. Water, which is an isocyanate-reactive material,also functions as a blowing agent if present in sufficient quantities,because it reacts with isocyanate groups to liberate carbon dioxide,which then serves a blowing gas. However, other chemical and/or physicalblowing agents can be used instead of or in addition to water. Chemicalblowing agents react under the conditions of the elastomer-forming stepto produce a gas, which is typically carbon dioxide or nitrogen.Physical blowing agents volatilize under the conditions of thepolymer-forming step. Suitable physical blowing agents include variouslow-boiling chlorofluorocarbons, fluorocarbons, hydrocarbons and thelike. Fluorocarbons and hydrocarbons having low or zero global warmingand ozone-depletion potentials are preferred among the physical blowingagents.

In addition, a gas such as carbon dioxide, air, nitrogen or argon may beused as the blowing agent in a frothing process.

The amount of blowing agent can vary considerably, depending on theparticular blowing agent used and the desired density of the resultingpolymer.

Cell openers are often present in flexible foam formulations. Cellopeners include high molecular weight (generally 4000-20,000 MW)polyethers, typically having ethylene oxide contents of at least 40%,preferably at least 50% by weight.

One or more fillers may also be present. A filler may help modify thecomposition's rheological properties in a beneficial way, reduce costand impart beneficial physical properties to the polymer. Suitablefillers include particulate inorganic and organic materials that arestable and do not melt at the temperatures encountered during thepolyurethane-forming reaction. Examples of suitable fillers includekaolin, montmorillonite, calcium carbonate, wollastonite, talc,high-melting thermoplastics, glass, fly ash, carbon black, titaniumdioxide, iron oxide, chromium oxide, azo/diazo dyes, phthalocyanines,dioxazines, colloidal silica and the like. The filler may impartthixotropic properties. Fumed silica is an example of such a filler.When used, fillers advantageously constitute from about 0.5 to about30%, especially about 0.5 to about 10%, by weight of the polymer.

Some of the foregoing fillers may also impart color to the polymer.Examples of these include titanium dioxide, iron oxide, chromium oxideand carbon black. Other colorants such as azo/diazo dyes,phthalocyanines and dioxazines also can be used.

Reinforcing agents may also be present. The reinforcing agents take theform of particles and/or fibers that have an aspect ratio (ratio oflongest dimension to shortest dimension) of at least 3, preferably atleast 10. Examples of reinforcing agents include mica flakes, fiberglass, carbon fibers, boron or other ceramic fibers, metal fibers,flaked glass and the like. Reinforcing agents may be formed into mats orother preformed masses.

It is also possible to include one or more catalysts for the reaction ofan isocyanate group with an alcohol, primary amine or secondary aminegroup, in addition to the bismuth mono- or dithiocarbamate or mono- ordithiocarbonate salt.

Suitable such additional catalysts include, for example:

-   -   i) certain tertiary phosphines such as a trialkylphosphine or        dialkylbenzylphosphine;    -   ii) certain chelates of various metals, such as those which can        be obtained from acetylacetone, benzoylacetone, trifluoroacetyl        acetone, ethyl acetoacetate and the like, with metals such as        Be, Mg, Zn, Cd, Pd, Ti, Zr, Al, Sn, As, Bi, Cr, Mo, Mn, Fe, Co        and Ni;    -   iii) certain acidic metal salts of strong acids, such as ferric        chloride, stannic chloride, stannous chloride, antimony        trichloride, bismuth nitrate and bismuth chloride;        strong bases, such as alkali and alkaline earth metal        hydroxides, alkoxides and phenoxides;    -   (iv) certain alcoholates or phenolate of various metals, such as        Ti(OR)₄, Sn(OR)₄ and Al(OR)₃, wherein R is alkyl or aryl, and        the reaction products of the alcoholates with carboxylic acids,        beta-diketones and 2-(N,N-dialkylamino)alcohols;    -   (v) certain alkaline earth metal, Bi, Pb, Sn or Al carboxylate        salts; and    -   (vi) certain tetravalent tin compounds, and certain tri- or        pentavalent bismuth, antimony or arsenic compounds.

In some embodiments, the bismuth salt is the sole metal-containingcatalyst in the formulation. In other embodiments, the bismuth salt isthe sole catalyst in the formulation.

The processing method used to make the polymer is not considered to becritical to the invention, provided that the isocyanate compound and theisocyanate-reactive material(s) are mixed and cured in the presence ofthe bismuth salt to form the polymer. The curing step is achieved bysubjecting the reaction mixture to conditions sufficient to cause theisocyanate compound and isocyanate reactive material(s) to react to formthe polymer.

Thus, for example, flexible and semi-flexible polyurethane foam can bemade in accordance with the invention in a slabstock or molding process.Flexible polyurethane foams are typically made using one or more polyolshaving an equivalent weight per hydroxyl group of at least 500 to about2200. Enough blowing agent is used to produce a foam having a density offrom 1 to 8 pounds/cubic foot (16-128 kg/m³), preferably from 1.5 to 4pounds/cubic foot (24-64 kg/m³). Water is a preferred blowing agent.Mixtures of water and a physical blowing agent can be used. Acrosslinker and/or chain extender are often present, preferably a polyolor aminoalcohol crosslinker having a molecular weight per isocyanatereactive group of from about 30 to about 75. Isocyanate indices formaking flexible polyurethane foam are typically from 70 to 125, moretypically from 85 to 115.

Slabstock foam is conveniently prepared by mixing the foam ingredientsand continuously dispensing them into a trough or other region where thereaction mixture reacts, rises freely against the atmosphere (sometimesunder a film or other flexible covering) and cures. In common commercialscale slabstock foam production, the foam ingredients (or variousmixtures thereof) are pumped independently to a mixing head where theyare mixed and continuously dispensed onto a conveyor that is lined withpaper or plastic. Foaming and curing occurs on the conveyor to form afoam bun. High resilience slabstock (HR slabstock) foam is made usingmethods similar to those used to make conventional slabstock foam. HRslabstock foams are characterized in exhibiting a Bashore rebound scoreof 55% or higher, per ASTM 3574-03.

Molded foam can be made according to the invention by mixing the foamingredients and transferring the resulting reaction mixture to a closedmold where the foaming reaction takes place to produce a shaped foam.Either a so-called “cold-molding” process, in which the mold is notpreheated significantly above ambient temperatures, or a “hot-molding”process, in which the mold is heated to drive the cure, can be used.Cold-molding processes are preferred to produce high resiliency moldedfoam.

Rigid polyurethane foam can be made in accordance with the invention.Rigid foam can be made in a pour-in-place process, as is often the casewhen the foam forms a thermal insulation layer in an appliance, cooleror other structure. Rigid foam also can be produced using pouringprocesses or sheet-forming processes. Rigid polyurethane foams aretypically made using polyols and/or aminoalcohols having an averageequivalent weight per hydroxyl group of at from about 40 to about 250,preferably from about 50 to about 125. Enough blowing agent is used toproduce a foam having a density of from 1 to 8 pounds/cubic foot (16-128kg/m³), preferably from 1.5 to 4, pounds/cubic foot (24-64 kg/m³). Wateris a preferred blowing agent. Mixtures of water and a physical blowingagent can be used. Isocyanate indices for making rigid polyurethane foamare typically from 90 to 200. Indices of from 150 to 600 are often usedwhen isocyanurate foams are to be produced.

Noncellular flexible and semi-flexible polyurethane and/or polyureamolded polymers can be made using various molding processes such asreaction injection molding, so-called SRIM or RRIM processes, variousspray molding methods, and the like. In these systems, theisocyanate-reactive material is typically a mixture that includes one ormore polyols and/or polyamines having a molecular weight perisocyanate-reactive group of at least 500, preferably at least 1200, toabout 3000, preferably to about 2500, and at least one chain extender.Blowing agents are usually absent or used in very small amounts, so thatthe density of the resulting polymer is at least 500 kg/m³. Isocyanateindices are typically from 90 to 125, preferably from 95 to 115.

The bismuth salt, or mixture of the bismuth salt and activator compound,is especially useful in processes in which a delayed cure is needed dueto processing constraints or for other reasons. Examples of theseprocesses include certain sealant and adhesive applications, certaincarpet backing or other textile-backing applications, and certain castelastomer processes. Sealants and adhesives are often required to havean “open time” of 2 to 60 minutes or more, to allow the material to bedispensed and the substrate(s) brought into position. Similarly, an opentime is often required in carpet backing and other textile backingprocesses, because the reaction mixture must remain flowable long enoughfor it to be spread across the surface of the carpet or textile andgauged to a needed thickness. Cast elastomer processes often need asignificant open time to allow for degassing or frothing, if desired,and mold filling. In all of these processes, it is preferable to obtaina rapid cure after the necessary open time has passed. In suchprocesses, the bismuth salt preferably is the sole metal-containingcatalyst (other than, optionally, an organic base activator in amountsas described before).

Carpet and other textile cushion backings can be made in accordance withthe invention via a mechanical frothing process. In such processes, air,nitrogen or other gas is whipped into the reaction. The frothed reactionmixture is then typically applied to a substrate where it is permittedto cure to form an adherent cellular layer. Such textile-backingprocesses are described, for example, in U.S. Pat. Nos. 6,372,810 and5,908,701.

Cast elastomers are generally made using a prepolymer orquasi-prepolymer as the isocyanate-reactive compound. The prepolymer orquasi-prepolymer is prepared by reacting an excess of a polyisocyanatewith at least one polyol that has a molecular weight of at least 400,preferably at least 800. The polyol(s) may have a molecular weight ashigh as about 12,000. A preferred molecular weight is up to 4000 and amore preferred molecular weight is up to 2000. The polyol(s) used inmaking the prepolymer or quasi-prepolymer preferably have an average offrom 1.8 to 3.0, preferably from 1.8 to 2.5 and still more preferablyabout 1.9 to 2.2 hydroxyl groups per molecule. A preferred polyol forthis application is an ethylene oxide-terminated polypropylene oxidediol or triol, or a mixture thereof with at least one poly(propyleneoxide) homopolymer diol or triol.

A low (up to 300) molecular weight diol may be used to make theprepolymer or quasi-prepolymer, in addition to the foregoingingredients. This low molecular weight diol preferably has a molecularweight of from 62 to 200. Examples of the low molecular weight diolinclude ethane diol, 1,2- or 1,3-propane diol, diethylene glycol,dipropylene glycol, triethylene glycol, tripropylene glycol,cyclohexanedimethanol, and the like. This material is usually used insmall amounts, if at all. If used in making the prepolymer orquasi-prepolymer, from 1 up to 25 parts by weight thereof may be usedper 100 parts by weight of the polyol(s) that have a molecular weight of400 or more.

The polyisocyanate used to make the prepolymer or quasi-prepolymerpreferably contains an average of from 1.8 to 3.5, more preferably from1.8 to 2.5 isocyanate groups per molecule and an isocyanate content ofat least 25% by weight. Aliphatic polyisocyanates are preferred whenlight stability is needed. In other cases, TDI, MDI, polymeric MDI or anMDI derivative is often useful. MDI may be the 2,2′-, 2,4′- or4,4′-isomer, with the 4,4′-isomer, or mixtures of the 4,4′- and2,4′-isomer, being preferred. “Derivatives” of MDI are MDI that has beenmodified to include urethane, urea, biuret, carbodiimide, uretonimine orlike linkages, and which have an isocyanate content of at least 25% byweight.

At least two equivalents of the polyisocyanate are used per equivalentof the diol(s) to make a prepolymer. More than two equivalents of thepolyisocyanate, typically at least 2.2 equivalents, are used perequivalent of the diol(s) used to make a quasi-prepolymer. The resultingproduct includes molecules formed by capping the diol(s) with thepolyisocyanate and, in the case of quasi-prepolymer, some quantity ofunreacted polyisocyanate. The prepolymer or quasi-prepolymer should havean isocyanate content of at least 4%, and preferably at least 8% byweight. The isocyanate content should not exceed 20% and preferably doesnot exceed 18% by weight. The prepolymer or quasi-prepolymer shouldcontain an average of from about 1.9 to about 2.5, preferably from 1.9to 2.3 and more preferably from 2.0 to 2.2 isocyanate groups permolecule.

The reaction to produce the prepolymer or quasi-prepolymer can becatalyzed. The catalyst may be a bismuth salt in accordance with thisinvention, or mixture thereof with an activator compound.

A cast elastomer is formed by mixing the prepolymer or quasi-prepolymerwith a chain extender and/or mixture of chain extender and at least onepolyol having a molecular of at least 400, as described with respect tothe prepolymer or quasi-prepolymer, and allowing the mixture to cure inthe presence of the bismuth thiophosphoric acid diester salt (or bismuthsalt/activator mixture) in a mold. The mold may be open or closed.

The chain extender may constitute from 2 to 100%, preferably from 4 to50 and still more preferably from 4 to 25%, of the combined weight ofthe combined weight of chain extender(s) and polyols having a hydroxylequivalent weight of at least 250.

To prepare the cast elastomer, the starting materials are generallymixed in ratios that produce an isocyanate index of at least 70 to about130. A preferred isocyanate index is from 80 to 120, and a morepreferred index is from 90 to 110.

The curing conditions are not generally considered to be criticalprovided that the mixture cures adequately. The components or themixture may be preheated before being introduced into the mold. The moldmay be preheated. It is usually necessary to cure the mixture atelevated temperature; for that reason the filled mold is generallyheated in an oven or other suitable apparatus. Mold temperatures may befrom 40 to 90° C. Curing times can range from as little as one minute to60 minutes or more. After curing at least to the extent that theresulting elastomer can be removed from the mold without permanentdamage or permanent deformation, the part can be demolded. If necessary,the part can be post-cured at an elevated temperature to complete thecure.

The elastomer will of course take the shape of the internal cavity ofthe mold; therefore the mold is designed to produce a part having thedesired external shape and dimensions. A wide range of elastomeric partscan be produced, including gaskets, bushings, wheels, belts, and thelike. However, shoe soles are an application of particular interest. Theshoe sole may be, for example, a midsole, an insole, and outsole, or anintegrated sole that performs two or more of these functions.

The cast elastomer may be produced at a density of as low as about 300kg/m³, preferably at least 500 kg/m³ by frothing the reaction mixturebefore curing it, or by including a blowing agent in the formulation.Microcellular cast elastomer made in such a way can be used, forexample, as shoe soles. Suitable frothing methods are described in U.S.Pat. Nos. 3,755,212, 3,849,156 and 3,821,130. Substantially non-cellularcast elastomers may be produced using no blowing agent or frothing.

In cast elastomer processes, the bismuth salt often provides a long opentime followed by a rapid cure. The physical properties of the resultingelastomer are often comparable to those obtained using conventionalmercury catalysts.

The bismuth catalyst of the invention has the further advantage of beinghaving good stability in a polyol mixture. This is a very importantadvantage because it is common in the polyurethanes industry to produceformulated polyol mixtures that contain the catalyst(s), and to storethose formulated polyol mixtures for a period of time ranging from a fewhours or from about one day to up to several months. Thus, the bismuthcatalyst of this invention can be blended with one or moreisocyanate-reactive compounds, preferably one or more polyols, to form aformulated polyol mixture, which is then stored for a day or more beforebeing reacted with the polyisocyanate to form a polymer.

It is also possible to blend the bismuth catalyst of the invention intoa polyisocyanate to produce a formulated polyisocyanate mixture thatcontains the catalyst. Such a formulated polyisocyanate mixture also hasgood stability, and can be stored for a period of time ranging from afew hours or from up about one day up to several months.

The following examples are provided to illustrate the invention but arenot intended to limit the scope thereof. All parts and percentages areby weight unless otherwise indicated.

Examples 1 and 2 Comparative Samples A and B

A catalyst solution is prepared by dissolving 0.2 parts of bismuth (III)tris(di-n-hexyldithiocarbamate) in 0.8 parts of tripropylene glycol and1 part of 3,7-dimethyloctanol.

Example 1

A masterbatch of 7774 parts of a 6000 molecular weight, ethyleneoxide-capped poly(propylene oxide) triol, 1078 parts of 1,4-butane dioland 177 parts of an aluminosilicate molecular sieve paste is blended ina mechanical mixer. A 66.6 part sample of this masterbatch is dispensedinto a plastic cup suitable for use on a FlakTex Speedmixer. 0.43 partsof the catalyst solution are added to the masterbatch, and the mixtureis mixed on the Speedmixer for 90 seconds. Then, 34.5 parts of amodified MDI having an isocyanate functionality of about 2.1 is mixedinto the polyol mixture for 60 seconds. The reaction mixture is thenpoured into a steel plaque mold that is sprayed with an external moldrelease and preheated to 80° C. Tack-free and demold times are measured.Tack-free time is the time after pouring at which the composition nolonger sticks to a metal spatula touched to its surface. Demold time isthe amount of time necessary before the part can be demolded withoutdamage. Following demold, the parts are postcured for 1 hour at 80° C.in a forced air oven and allowed to sit for one day at room temperature.Tensile properties and Shore A hardness are then measured according toASTM D7108. Results are as indicated in Table 1.

Example 2

This sample is made in the same manner as Example 1 except the amount ofcatalyst solution is increased to 0.59 parts. Results are as indicatedin Table 1.

Comparative Sample A:

Comparative Sample A is made in the same general manner as Example 1,except the catalyst is 0.18 parts of a titanium catalyst complex soldcommercially as Snapcure™ 2210 by Alfa Aesar, a Johnson Matthey company.

Comparative Sample B is prepared by mixing 7 g of the polyol masterbatchwith 50 microliters of a solution of 25.8 millimoles of bismuthtris(dodecylmercaptan) in 4 mL toluene. This provides 0.323 millimolesof catalyst. About 3.5 g of a 160.1 isocyanate equivalent weighturetonimine-modified diphenylmethane diisocyanate that has an average of2.1 isocyanate groups per molecule is added. This time is designatedt=0. The resulting mixture is stirred at room temperature for twominutes forty-five seconds, and then poured into a preheated (80° C.)pan to form a layer 2 mm thick. Tack-free time is evaluated byperiodically touching the top of the reaction mixture with a spatula.The tack-free time is the time at which no material sticks to thespatula. The sample is aged at 80° C. for one hour and its Shore Ahardness is measured.

Results of the testing are indicated in Table 1.

TABLE 1 Comp. Comp. Sample Sample Property Example 1 Example 2 A BCatalyst Bi tris(di- Bi tris(di- Titanium Bi tris- n-hexyl n-hexyl(dodecyl dithio- dithio- mercaptan) carbamate) carbamate) Catalystamount, 0.43 0.59 ND 31 mmol/kg reactants Tack-free time, 6 5:20 4 9minutes:seconds Demold time, 16 9 5:30 12:30 minutes:seconds 100%Modulus, 20.8 18.6 21.5 ND MPa Tensile strength, 16.5 18.8 17.4 ND MPaElongation at 383 429 347 ND break, % Shore A Hardness 89 89 87 80-85 ND= not determined.

The bismuth dithiocarbamate salt provides a long open time followed by arapid cure. Cure is faster at the higher concentration of bismuthdithiocarbamate salt, at the expense of some pot time (as indicated bythe tack-free time). The physical properties of Examples 1 and 2 arecomparable to those provided by the titanium catalyst (ComparativeSample A). The bismuth mercaptide catalyst (Comp. Sample B) providesvery long tack-free times and a softer polymer under this test.

Example 3

A catalyst solution is prepared by dissolving 0.2 parts of bismuth (III)tris(octyl dithiocarbonate) in 0.8 parts of tripropylene glycol and 1part of 3,7-dimethyloctanol. An elastomer is made in the same manner asdescribed with respect to Example 1, substituting 0.18 g of thiscatalyst solution for that used in Example 1. Properties are measured asdescribed with respect to Example 1. Results are as indicated in Table2.

TABLE 2 Property Example 1 Catalyst Bi tris(octyl xanthate) Catalystamount, 0.22 mmol/kg reactants Tack-free time, minutes 5.3 Demold time,minutes 9 100% Modulus, MPa 23.2 Tensile strength, MPa 18.0 Elongationat break, % 396 Shore A Hardness 89

The bismuth dithiocarbonate catalyst provides a long open time followedby a rapid cure, and produces a polymer having properties very similarto those of Comparative Sample A.

Examples 4-10 and Comparative Samples C-E

A polyol mixture is formed from 0.819 parts of 1,4-butanediol and 6.181g of a 6000-molecular weight, nominally trifunctional polyether polyolobtained by adding propylene oxide and then ethylene oxide to glycerinin the presence of potassium hydroxide catalyst. 2% by weight of analuminosilicate molecular sieve paste are added. A catalyst solution isprepared by dissolving bismuth tris(dihexyl dithiocarbamate) in enoughtoluene to produce a catalyst solution containing 10 mg of catalyst permL of solvent.

7 g of this polyol mixture are weighed into a vial. For Example 4, 50microliters of the catalyst solution is added to the vial and mixed in.About 3.5 g of a 160.1 isocyanate equivalent weight uretonimine-modifieddiphenylmethane diisocyanate that has an average of 2.1 isocyanategroups per molecule is added. This time is designated t=0. The resultingmixture is stirred at room temperature for one minute. The vial contentsare then visually monitored. Tack-free time is evaluated by periodicallytouching the top of the reaction mixture with a spatula. The tack-freetime is the time at which no material sticks to the spatula. Results areas indicated in Table 3.

Examples 5 and 6 are prepared in the same manner, except the amount ofcatalyst solution in Examples 5 and 6 are 1 mL and 1.5 mL, respectively.Whitening and tack-free times for Examples 5 and 6 are indicated inTable 3.

Plaques are also made from the Example 6 formulation, by adding thecatalyst solution to the polyol mixture, stirring in the polyisocyanatefor one minute and pouring the reaction mixture onto a 70 mm circularaluminum pan on an 80° C. hot plate. Tack-free time is evaluated asbefore. Results are in indicated in Table 3.

Example 7 is prepared in the same manner as Example 4, except themolecular sieves are omitted and the amount of catalyst is increased asindicated in Table 3.

Examples 8-10 are prepared in the same manner as Example 4, except themolecular sieves are replaced with varying amounts of a zeolite which isdried overnight at 300° C.), and the amount of catalyst is changed asindicated in Table 3.

Comparative Samples C and D each are the same as Example 7, except thecatalyst in each case is 0.25 micromoles of bismuth tris(2-ethylhexanoate). In Sample C, the catalyst is blended with the polyolmixture, and the mixture is then held for about 2 hours at roomtemperature before adding the polyisocyanate. In Sample E, the catalystis blended with the polyol mixture, which is then held for about 20hours at room temperatures before adding the polyisocyanate. ComparativeSample E is the same as Comparative Sample E, except 82 mg of a zeoliteare present.

TABLE 3 Tack- Exam- Bi catalyst free ple Bi (mmol/kg Activator Activatortime No. catalyst type reactants) Type Amount (min:sec) 4 tris (dihexyl0.048 Molecular 2 wt-% 12:20 dithiocarbamate) Sieves 5 tris (dihexyl0.096 Molecular 2 wt-%  7:36 dithiocarbamate) Sieves 6 tris (dihexyl0.144 Molecular 2 wt-%  6:15 dithiocarbamate) Sieves 6 tris (dihexyl0.144 Molecular 2 wt-%  3:40 (plaque, dithiocarbamate) Sieves 80° C.) 7tris (dihexyl 0.190 None 0 >20 dithiocarbamate) 8 tris (dihexyl 0.190Zeolite  22 mg  8:45 dithiocarbamate) 9 tris (dihexyl 0.190 Zeolite  62mg  6:40 dithiocarbamate) 10  tris (dihexyl 0.190 Zeolite 117 mg  6:50dithiocarbamate) Comp. tris(2-ethyl 0.024 None 0  6:40 Sample.hexanoate) C Comp. tris(2-ethyl 0.024 None 0 11:00 Sample hexanoate) DComp. tris(2-ethyl 0.024 Zeolite  82 mg  6:40 Sample hexanoate) E

Example 7 shows that the bismuth dithiocarbamate catalyst provides avery slow cure in the absence of an activator. Examples 4-10 show theeffect of activators (molecular sieves or zeolite) and varying catalystlevel. In the presence of the activator, the bismuth dithiocarbamatecatalyst provides effective curing even at low levels. ComparativeSamples C-E demonstrate the performance of a conventional bismuthcarboxylate catalyst. That catalyst cures the mixture even without anactivator (Comp. Sample C). However, the catalyst deactivates uponstanding in a polyol mixture, as shown by the long tack-free time ofComparative Sample D, in which the catalyst/polyol blend is stored forless than a day before curing the mixture. In addition, the bismuthcarboxylate catalyst performance is not affected by the presence of anactivator (Comparative Sample E). Therefore, the performance of thisbismuth carboxylate catalyst cannot be “tuned” using activatorcompounds, as can the bismuth catalysts of this invention.

Examples 11-13

A catalyst solution is prepared by dissolving bismuth tris(octyldithiocarbonate) in enough toluene to produce a solution containing 10mg of catalyst per mL of solvent. Examples 11-13 are made in the samemanner as described with respect to Example 4. In Example 11, enough ofthis solution is added to provide 0.25 mg of the catalyst. In Examples12 and 13, enough of the solution to provide 1.1 and 2 mg of thecatalyst, respectively, is added. A plaque also is made from the Example11, in the manner described with respect to Example 6. Tack-free timesare measured, and are as indicated in Table 4.

TABLE 4 Bi catalyst Bi catalyst Tack-free Example No. (mg) (mmol/kgreactants time (min 11 0.25 0.029 9.2 11 (plaque, 80° C.) 0.25 0.029 3.712 1.1 0.127 3.4 13 2 0.231 4.8

Examples 14-17

A polyol mixture is formed from 0.819 parts of 1,4-butanediol and 6.181g of a 6000-molecular weight, nominally trifunctional polyether polyolobtained by adding propylene oxide and then ethylene oxide to glycerinin the presence of potassium hydroxide catalyst.

Catalyst Solution A contains bismuth tris(dihexyl dithiocarbamate) inenough toluene to produce a solution that contains 10 mmoles of thecatalyst per liter of solution. Catalyst solution B is a toluenesolution that contains 10 mmoles of bismuth tris(octyl dithiocarbonate)per liter.

Example 14

7 g of the polyol mixture is weighed into a vial. 200 microliters ofCatalyst Solution A are added to the vial and mixed in. About 3.5 g of a160.1 isocyanate equivalent weight uretonimine-modified diphenylmethanediisocyanate that has an average of 2.1 isocyanate groups per moleculeis added. This time is designated t=0. The resulting mixture is stirredat room temperature for 30 seconds. The vial contents are then visuallymonitored. As the mixture begins to cure, an opaque area first forms atthe surface of the mixture. The time at which this area first forms isdesignated as the “whitening time”. Tack-free time is evaluated byperiodically touching the top of the reaction mixture with a spatula.The tack-free time is the time at which no material sticks to thespatula. Results are as indicated in Table 5.

Example 15 is the same as Example 14, except that 60 microliters of a1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) solution in toluene is added.This DBU solution contains 33.5 millimoles DBU per liter of solution.

Examples 16 and 17 are the same as Examples 14 and 15, respectively,except Catalyst Solution A is replaced with 100 microliters of CatalystSolution B in each case.

Whitening and tack-free times for each of Examples 14-17 are asindicated in Table 5.

TABLE 5 Bi Catalyst Amount DBU (mmol/kg (mmol/kg Whitening Tack-free Ex.of of Time, Time, No. Type reactants) reactants) min:sec min:sec 14bismuth 0.190 0 8 >20 tris(dihexyl dithiocarbamate) 15 bismuth 0.1900.191 5:30 7:50 tris(dihexyl dithiocarbamate) 16 Bismuth 0.095 09:30 >20 tris(octyl dithiocarbonate) 17 Bismuth 0.095 0.191 6:15 8:50tris(octyl dithiocarbonate)

As can be seen from the data in Table 5, the bismuth salts by themselvesprovide very slow cures. The addition of the tertiary amine (DBU) invery small amounts leads to a significant decrease in cure times. At thesmall amounts present in Examples 15 and 17, DBU by itself providestack-free times in excess of 20 minutes. Therefore, the reduction incure times seen in Examples 15 and 17 are not attributable to thecatalytic effect of the DBU. Instead, the DBU is believed to befunctioning as an activator for the bismuth catalyst.

What is claimed is:
 1. A process for preparing a polyisocyanate-basedpolymer, comprising forming a reaction mixture containing at least onepolyisocyanate, at least one isocyanate-reactive compound having atleast two isocyanate-reactive groups and at least one catalyst, and thencuring the reaction mixture in the absence of a blowing agent orfrothing to form the polyisocyanate-based polymer, wherein the catalystincludes a bismuth salt of a mono- or dithiocarbonate compound, whereinthe polyisocyanate-based polymer is a non-cellular cast elastomer, thepolyisocyanate is a prepolymer or quasi-prepolymer having an isocyanatecontent of 8 to 18% by weight and the isocyanate-reactive compound is achain extender or mixture of a chain extender and at least one polyolhaving a hydroxyl equivalent weight of at least
 250. 2. The process ofclaim 1 wherein the bismuth salt of a mono- or dithiocarbonate compoundhas the structure:

wherein X is sulfur or oxygen, X¹ is sulfur or oxygen, provided that atleast one of X and X¹ is sulfur, each R¹ is independently a hydrocarbylgroup that may be substituted with one or more heteroatom-containingsubstituent groups, n is a number from 1 to 3, and each L isindependently an anion other than a mono- or dithiocarbonate anion. 3.The process of claim 2, wherein n is at least 2 and both X and X¹ aresulfur.
 4. The process of claim 3, wherein n is
 3. 5. The process ofclaim 1 wherein the bismuth salt of a mono- or dithiocarbonate compoundis present in an amount from 0.01 to 3 millimoles per kilogram ofpolyisocyanate(s) and isocyanate-reactive material(s) present in thereaction mixture.
 6. The process of claim 5 wherein the bismuth salt ofa mono- or dithiocarbonate compound is present in an amount from 0.05 to1 millimole per kilogram of polyisocyanate(s) and isocyanate-reactivematerials) present in the reaction mixture.
 7. The process of claim 6wherein the reaction mixture contains at least one activator for thebismuth salt of a mono- or dithiocarbonate compound.
 8. The process ofclaim 7 wherein the activator includes at least one aluminosilicate. 9.The process of claim 7 wherein the activator includes at least oneinorganic or organic base.
 10. The process of claim 9 wherein theactivator is an amidine.
 11. The process of claim 10 wherein the amidineis present, in an amount of not more than 1 millimole per kilogram ofpolyisocyanate(s) and isocyanate-reactive materials) present in thereaction mixture.
 12. The process of claim 11 wherein the amidine ispresent in an amount from 0.1 to 5 moles per mole of the bismuth salt.13. The process of claim 11 wherein the amidine is present in an amountfrom 0.5 to 3 moles of tertiary amine activator per mole of the bismuthsalt of a mono- or dithiocarbonate compound.